Evaluation of the Perkins®handheld applanation tonometer in the measurement of intraocular pressure in dogs and cats

Abstract

To evaluate and to validate the accuracy of the Perkins handheld applanation tonometer in the measurement of IOP in dogs and cats. Twenty eyes from 10 dogs and 10 cats immediately after sacrifice were used for the postmortem study and 20 eyes from 10 clinically normal and anesthetized dogs and cats were used for the in vivo study. Both eyes of 20 conscious dogs and cats were also evaluated. Readings of IOP postmortem and in vivo were taken using manometry (measured with a mercury column manometer) and tonometry (measured with a Perkins handheld applanation tonometer). The IOP measurement with Perkins tonometer in anesthetized and conscious dogs and cats was accomplished by instillation of proxymetacaine 0.5% and of 1% fluorescein eye drops. The correlation coefficient (r(2)) between the manometry and the Perkins tonometer were 0.982 (dogs) and 0.988 (cats), and the corresponding linear regression equation were y = 0.0893x + 0.1105 (dogs) and y = 0.0899x + 0.1145 (cats) in the postmortem study. The mean IOP readings with the Perkins tonometer after calibration curve correction were 14.9 +/- 1.6 mmHg (range 12.2-17.2 mmHg) in conscious dogs, and were 15.1 +/- 1.7 mmHg (range 12.1-18.7 mmHg) in conscious cats. There was an excellent correlation between the IOP values obtained from direct ocular manometry and the Perkinstonometer in dogs and cats. The Perkins handheld tonometer could be in the future a new alternative for the diagnosis of glaucoma in veterinary ophthalmology.